The CMP runs what they call their "CMP Games Matches" at the Nationals at Camp Perry, and the John C. Garand Match is the biggest of these. Every year it seems to get bigger. All stages are fired at 200 yards, and it's relatively informal (although some folks are pretty serious about it). Last year, they had 1,177 shooters in just the Garand Match - lot of metal going into Lake Erie! Other matches in the CMP Games are an M1 Carbine Match and a Springfield 1903/Vintage Military Rifle Match. You can get more information on last year's events here. The program for this year is available here. One change this is year is the "unlimited Garand" category, which allows glass bedding and other improvements not previously allowed.

Some folks dress up in period uniforms. I know Gunny R. Lee Ermey participated last year, and I believe he has previously. Here's a picture of him at one of the matches.

NRA now has a similar match for the M14 and clones, the Springfield M1A Match.